期刊
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH
卷 257, 期 -, 页码 174-183出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jvolgeores.2013.03.026
关键词
Shield; Monogenetic; Basaltic volcano; Crypto-tephra; Auckland Volcanic Field
资金
- Marsden Fund grant [UOA0517]
- New Zealand Earthquake Commission
- Auckland City Council
The life-span of small volcanoes in terrestrial basaltic fields, commonly considered 'monogenetic', can be difficult to assess due to a paucity of datable materials capable of providing a 10(2)-10(2)-year age resolution. We have used microscopic tephra layers (crypto-tephra) in lake sediments to determine the longevity of Rangitoto volcano, a small shield that represents the most recent volcanism in the Auckland Volcanic Field (AVF), New Zealand. Previous studies suggested construction in a relatively short interval at similar to 550-500 cal yrs BP. In contrast, the tephra record shows evidence of intermittent activity from 1498 +/- 140 to (at least) 504 +/- 6 cal yrs BP, a longevity of similar to 1000 years. Rangitoto volcano is thought to represent about half the magma erupted in the 250-ka-history of AVF. Thus, the AVF has experienced a dramatic shift to prolonged and voluminous central-vent volcanism in its most recent history. This demonstrates the difficulty in determining time-erupted volume relationships in such fields. Previous AVF hazard-risk modeling based on isolated, short-lived (<1 year) phenomena at sites that have not experienced activity needs to be revisited in light of the new Rangitoto chronology. (C) 2013 Elsevier B.V. All rights reserved.
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